Power supply system method of use

ABSTRACT

A power supply system is provided that includes a power supply and at least one energy storage capacitor bank. A voltage monitor is coupled to the power supply and the energy storage capacitor bank. A feedback control is coupled to the power supply. The feedback control is configured to provide that a current applied to the energy storage capacitor bank is substantially the same as current leaking out of the power supply.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a continuation in part of U.S. Ser. No.11/053,194 filed Feb. 7, 2005 U.S. Pat. No. 7,276,857, and is acontinuation-in-part of U.S. Ser. No. 11/053,195, filed Feb. 7, 2005,both of which applications claim the benefit of priority from commonlyassigned co-pending U.S. Provisional Application Ser. No. 60/569,207filed May 6, 2004. All of the above-identified applications are fullyincorporated herein by reference for all purposes.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates generally to power supply systems, andmore particularly to power supply systems that charge one or more energystorage capacitor banks, and provide that a current applied issubstantially the same as current leaking out of the power supply.

2. Background Art

Power supplies and amplifiers are well known in the art. A variety ofconfigurations and topologies have been developed over the years toprovide electrical power to a load. Loads that have widely varyingimpedances, however, provide a challenge to traditional power suppliesdriven by conventional techniques. One particular challenge involvesfinding a power supply or amplifier capable of supplying a variety ofwaveforms to drive a dynamic, widely varying load such as a flash lamp.

Flash lamps are of particular interest because of the difficulty ofdriving a flash lamp is the very dynamic nature of the load. When aflash lamp varies impedance to a point where the impedance is lower thanthe output impedance of the flash lamp, more energy is dissipated in theamplifier than in the load. This may end up (in other topologies)heating up of switches and the energy is dissipated as heat. Forexample, as current is sourced through the lamp, the impedance of thelamp changes in a negative way. With a fixed impedance load, as currentis increased, the voltage drop across the fixed load proportionallyincreases also. With a flash lamp, this does not occur because the lampbecomes more conductive as more current is sourced into it. The voltagedrop stays the same or it may go down (this is known as negativeimpedance). For most amplifiers, this has an appearance of a dead shortoccurring on the output. It appears as a varying load that isapproaching a dead short at a very critical time. These qualities of aflash lamp make them particularly difficult to drive. Additionally, someknown power supplies heat the flash lamps too quickly which may resultin premature failure of the lamps.

Power supplies and amplifiers that can provide pulse width modulationoutput (PWM) are of particular interest. Some known configurations ortopologies that can provide a PWM output to control power include pushpull, bridge inverter, and flyback topologies. Known amplifiers withthese topologies may provide rectangular pulses delivered to atransformer at a regular period. However, these known power supplies userectangular pulses delivered to a transformer at a regular period andthrottle the duty cycle forwards or backwards (greater or less)depending on the current need of the load. Most switching power suppliesthat are in many common place items are driven to operate in thismanner.

Traditional resonant power supplies cannot provide variable energy perpulse. Rather the energy per pulse is fixed requiring fewer pulses perunit time be delivered to reduce output energy and more pulses per unittime to increase energy. This method in effect removes pulses which willcause the flash lamp to extinguish at low energy levels. Traditional PWMcontrolled power supplies use switch on time duty cycle to controlenergy and thus offer limited control range.

There is a need for a power system where an energy storage capacitorbank is charged, and then the amount of current applied to the energystorage capacitor is substantially the same as current leaking out ofthe power supply. There is a further need for a power system whereoutput of the power supply is rectified and used to charge the energystorage capacitor bank. There is a further need for a low repetitionrate power system where an energy storage capacitor bank is charged, andthen the amount of current applied to the energy storage capacitor issubstantially the same as current leaking out of the power supply.

SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is to provide a powersystem, where an energy storage capacitor bank is charged, and then theamount of current applied to the energy storage capacitor issubstantially the same as current leaking out of the power supply.

Another object of the present invention is to provide a low repetitionrate power system, where an energy storage capacitor bank is charged,and then the amount of current applied to the energy storage capacitoris substantially the same as current leaking out of the power supply.

A further object of the present invention is to provide a power systemwhere output of the power supply is rectified and used to charge anenergy storage capacitor bank.

Another object of the present invention is to provide a power systemwith an amplifier that is able to withstand the appearance of a deadshort occurring on the output amplifier.

A still further object of the present invention is to provide a powersystem with an amplifier which provides switching power supplies thatcan withstand a load having positive and negative impedance.

Another object of the present invention is to be able to provide a powersystem with an amplifier that can synthesize a variety of waveforms andpulses.

Yet another object of the present invention is to provide a power systemwith an amplifier that is scalable and modular.

A still further object of the present invention is to provide a powersystem with an amplifier that can be scalable, and being like batteries,can be connected in series, parallel, and series parallel.

Another object of the present invention is to provide a power systemwith high frequency PWM that goes directly to a lamp or other load anduses the duty cycle of the PWM to control the power delivered to theload.

Another object of the present invention is to provide a power systemthat can create a high frequency pulsed energy output directly to a lampor other load and modulate the frequency or period to control powerdelivery to the load.

These and other objects of the present invention are achieved in a powersupply system that includes a power supply. At least one energy storagecapacitor bank is provided. A voltage monitor is coupled to the powersupply and the energy storage capacitor bank. A feedback control iscoupled to the power supply. The feedback control is configured toprovide that a current applied to the energy storage capacitor bank issubstantially the same as current leaking out of the power supply.

In another embodiment of the present invention, a power supply system isprovided that has a power supply and at least one energy storagecapacitor bank. A voltage monitor is coupled to the power supply and theenergy storage capacitor bank. A feedback control is coupled to thepower supply. The feedback control is configured to provide that acurrent applied to the at least one energy storage capacitor bank issubstantially the same as current leaking out of the power supply. Adynamic load has a dynamic load impedance. An amplifier has a topologyconfigured to provide a PWM power output to the dynamic load. Theamplifier has an output impedance that is less than the impedance of theload when the load is in a confined discharge mode.

In another embodiment of the present invention, a power supply system isprovided and includes a power supply and at least one energy storagecapacitor bank. A voltage monitor is coupled to the power supply and theenergy storage capacitor bank. A feedback control is coupled to thepower supply. The feedback control is configured to provide that acurrent applied to the energy storage capacitor bank is substantiallythe same as current leaking out of the power supply. A dynamic load hasa dynamic load impedance. An amplifier has a topology configured toprovide a PWM power output to the dynamic load. The amplifier has anoutput impedance that is less than the impedance of the load when theload is in a confined discharge mode. A flash lamp is provided that hasa flash lamp impedance and an arc persistence time when the flash lampis lit. The amplifier has a topology for providing PWM power outputdirectly to the flash lamp. An amplifier driver is configured to drivethe amplifier. The amplifier driver has a fixed or variable frequencycontrol that provides the PWM power output at a frequency such that theperiod of the power output does not exceed the persistence time of aflash lamp during energy delivery.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1( a) is a schematic diagram illustrating one embodiment of a powersupply system of the present invention.

FIG. 1( b) is a schematic diagram showing various modules for oneembodiment of an amplifier that can be utilized with the FIG. 1( a)power supply system.

FIG. 2 is a graph of a PWM output to a load versus the analog inputsignal.

FIG. 3 shows a schematic of one embodiment of an inverter sectionaccording to the present invention.

FIG. 4( a) is a graph of drain voltage for a switch used in oneembodiment of the present invention.

FIGS. 4( b) and 4(c) are graphs of multiple variables such as loadcurrent, drain voltage, and gate drive for a switch used in oneembodiment of the present invention.

FIG. 5 shows a schematic for one embodiment of an amplifier according tothe present invention.

FIG. 6 shows an embodiment of the present invention where the outputs oftwo amplifiers are coupled together for a series drive configuration.

FIG. 7 shows an embodiment of the present invention where the outputs oftwo amplifiers are coupled together for a parallel drive configuration.

FIG. 8 shows an embodiment of the present invention where the outputs oftwo amplifiers are coupled together.

FIG. 9 shows an embodiment of the present invention where the outputs oftwo amplifiers are coupled together for series/parallel driveconfiguration.

FIG. 10 shows an embodiment of the present invention where the outputsof two amplifiers are coupled together for in-phase, series driveconfiguration.

FIGS. 11-14 are graphs illustrating certain embodiments of laser systemsof the present invention.

DESCRIPTION OF THE SPECIFIC EMBODIMENTS

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive of the invention, as claimed. It may be notedthat, as used in the specification and the appended claims, the singularforms “a”, “an” and “the” include plural referents unless the contextclearly dictates otherwise. Thus, for example, reference to “a material”may include mixtures of materials, reference to “a resistor” may includemultiple resistors, and the like. References cited herein are herebyincorporated by reference in their entirety, except to the extent thatthey conflict with teachings explicitly set forth in this specification.

In this specification and in the claims which follow, reference will bemade to a number of terms which shall be defined to have the followingmeanings:

“Optional” or “optionally” means that the subsequently describedcircumstance may or may not occur, so that the description includesinstances where the circumstance occurs and instances where it does not.For example, if a device optionally contains a feature for using afiltering device, this means that the filter feature may or may not bepresent, and, thus, the description includes structures wherein a devicepossesses the filtering feature and structures wherein the filteringfeature is not present.

Referring to FIGS. 1( a) and 1(b), one embodiment of the presentinvention is a power supply system 10 that includes a power supply 12.At least one energy storage capacitor bank 14 is provided. It will beappreciated that a plurality of energy storage capacitor banks 14 can beutilized. A voltage monitor 16 is coupled to the power supply 12 and theenergy storage capacitor bank 14.

A feedback control 18 includes control logic. In the case of a load, thefeedback control 18 measures and controls and amount of energy deliveredto the load. In this embodiment, the feedback control 18 measures theamount of energy that is delivered to a pulse forming network. Thefeedback control 18 then goes into a high resolution mode where itmaintains the amount of energy stored in the pulse forming network. Thiscompensates for internal losses within the pulse forming network thatoccur through component imperfections. The high resolution mode meansthat it can measure much smaller changes in the energy storage level. Aprecision control device is included in the feedback control, as morefurther shown in FIG. 1( b). This is an additional input into block 50.It measures load voltage. is coupled to the feedback control 18 and thepower supply 12. The feedback control 18 is configured to provide that acurrent applied to the energy storage capacitor bank 14 is substantiallythe same as current leaking out of the power supply 12. In oneembodiment, power supply system 10 is coupled to an amplifier 20.

As illustrated in FIG. 1( b), one method of using amplifier 20 is toprovide energy to a dynamic, non-linear load such as any pulseddischarge system, including but not limited to electro-optics devices,lasers, flash lamps, welding equipment, medical equipment such asdefibrillators, and the like. As seen in FIG. 2, the amplifier 20 canuse PWM to control the amount of power delivered to the load over time.

In one specific embodiment of the present invention, a lamp 22, whichagain is a particular type of load, is provided that filters the pulsednature of an output of the amplifier 20, and produces light output,which is proportional to the PWM duty cycle. The power output of thelamp 26 is shown by curve 110 in FIG. 2( b). The output from theamplifier 20 to the lamp 26 is shown as a plurality of pulses 112.

In one embodiment, the train of pulses 112 are at a fixed period 120 butvariable duty cycle (ON-to-OFF state ratio) is delivered to the load 22.In other words, as seen in FIG. 2( b), the amount of time in each period120 is fixed, but the amount of time that power (i.e. pulses 112) isdelivered during each period 120 is variable. As the duty cycle ON timeis increased, the power delivered to the load 22 increases. In FIG. 2,this is indicated by the “wider” pulse 122 and the increased amplitudeof line 110. It should be understood that the amplifier 20 varies theduty cycle in response to an analog signal presented to the input andthus functions as an amplifier. For example, to provide a sinusoidalpower waveform, the width of the pulses are varied. The pulses 122 arethe actual energy being delivered to the lamp. In this embodiment, theperiod 120 is constant. Width of pulse 122 is the amount of time theswitches are ON which determines the amount of power (energy/seconds)delivered to the lamp during the given pulse. In FIG. 2, the pulse ONtimes (widths) are increased at a sinusoidal rate and thus the powerenvelope delivered to the lamp is sinusoidal as indicated by line 110.

For a flash lamp driven by the amplifier 20 according to the presentinvention, the period 120 is determined in part by the persistence timeof the lamp 22. The persistence time is the length of time that thestreamer in the lamp remains intact. In other words, it is the amount oftime it takes for the gas in the lamp 22 to recombine, ionization tocease, and the streamer to decay and extinguish. Knowing that timeallows us to know what the maximum period (i.e. lowest PWM frequency)could be. The period, along with the lamp persistence time alsodetermines the amount of ripple in the light output from the lamp. Justas the lamp integrates the pulse train of the PWM into a smooth curvewith some ripple, the laser rod integrates the optical ripple. For thepresent invention used to drive a flash lamp load 22, the length of eachPWM period 120 should not exceed the persistence time of the flash lampor else the lamp will need to be re-lit (i.e. charging the gas until thestreamer reforms). Reducing the frequency (increasing period betweenpulses) will cause the streamer to extinguish.

In one embodiment, the period 120 may be about 1/10 the persistence timeof the lamp, to minimize ripples in the optical output of the lamp. Itshould be understood that other time periods may also be selected, suchas but not limited to 20% of the persistence time. Shorter time periodsmay be used without loss of the lamp streamer. Longer time periods (upto 100% of the persistence time) will introduce more ripple in theoptical output of the lamp. It should be understood of course, that insome embodiments, the period is not fixed and may be of variable length,preferably not exceeding the arc persistence time when used to drive alamp.

Referring again to FIG. 1( b), one embodiment of amplifier 20 accordingto the present invention will now be described. FIG. 2 shows that thisembodiment of the amplifier 20 may have four basic circuit elements: aninput section 140, a control section 150, a switch section 160, and anoutput section 170. In this embodiment, the switch section 160 receivesDC power from a power factor corrected (PFC) front end 162. The inputsection 140 provides signal amplification and scaling of the inputsignal and generates a proportional pulse width modulated (PWM) output.In this embodiment, the control section 150 manages the output energyfrom the output section 170 by regulating the ON time of the PWMgenerated in the input section 140. The ON time of the switch section160 will determine the amount of energy delivered to the load 22 duringeach PWM period from the output section 170. The control section 150also manages the overall pulse width and pulse repetition rate by gatingbursts of the smaller PWM pulses.

In another embodiment of the present invention, power supply system 10includes a load 22 that has a dynamic load impedance. In one embodiment,amplifier 20 is provided has a topology configured to provide a PWMpower output to the load 22. The amplifier 20 has an output impedancethat is less than the impedance of the load 22 when the load 22 is in aconfined discharge mode.

Referring now to FIG. 3, the inverter portion of the present inventionwill be described in further detail. The inverter provides the switchingand energy transfer elements controlled by control section 150. FIG. 3shows that in this embodiment, the inverter section comprises a resonantreset, forward converter topology. This topology provides the benefitsof typical non-resonant topologies such as PWM control, reasonableload/line variation tolerance and zero current on time switching.However, like a resonant topology, this design uses self-resonance toreset the core of transformer 182, which results in efficient off timeswitching. FIG. 3 shows a simplified schematic depicting the switchsection 160 and output section 170 (the sections are denoted by brokenlines) in the inverter section. The present topology includes at leastone MOSFET switch 180 in switch section 160 and a forward invertertransformer 182 in the output section 170 that is used to transferenergy to the load 22.

As seen in the embodiment of FIG. 3, when the MOSFET switch 180 isdriven high to a voltage above threshold, the switch 180 saturates andprovides conduction from the drain to source. Current then flows throughthe MOSFET switch 180 and the primary of the transformer 182 inducingload current in the output section 170 to the load 22. As seen in thewaveforms presented in FIG. 4( a), load current flows while the MOSFETswitch is ON (saturated). The energy delivered to the load 22 iscontrolled by the on time duration of the MOSFET gate drive signal. FIG.4( b) shows load current for a gate drive duration of 2.4 μS and FIG. 4(c) shows load current for a gate drive duration of 5 μS.

Once the MOSFET drive signal is turned off, the core of transformer 182is reset by returning the magnetizing current to the front end reservoirsection through the resonant circuit consisting of the MOSFET Millercapacitance, the transformer primary inductance, and the transformerinter-winding capacitance. During this reset period there is no currentflow in the MOSFET switch. This zero current switching enhances theoverall electrical efficiency of the amplifier 20. This minimizes theamount of energy that is dissipated by the amplifier 20 or returned tothe reservoir. During this time, the output of the amplifier 20 iselectrically isolated from the load 22. The diode D1 is used in thisembodiment to enable the electrical isolation.

The quantity of energy delivered to the load 22 is proportional to thelength of time that the switch 180 remains ON. The control logic in thecontrol section 150 manages the output energy of the amplifier 20 byvarying the ON time of switch 180. The maximum switch ON time limitoccurs when the core of transformer 182*82 saturates and that is afunction of the transformer design. If the ON time reaches this limit,the switch current will exceed the capability of the MOSFET and thedevice will be destroyed. The ON time limit in the embodiment of FIG. 5is 5 μS. Once the desired amount of energy is delivered, the gate ofswitch 180 is driven low to about 0 volts at which time the transformercore is reset.

FIG. 4( a) shows an oscilloscope image of the switch 180*80 drainvoltage during switching at maximum duty cycle. To achieve the desiredoutput, the present invention balances between all of the activecomponents, working with the MOSFETS and their miller capacitance andthe inductance available in a given size core in a transformer 182.Then, it is desirable to try to match that on the output side to a flashlamp. The switch section 160 and output section 170 should be compatiblewith the dynamic impedance of the flash lamp.

It should also be understood, however, that the maximum ON time (energy)for switch 180 is limited in part by the magnetic flux density of thetransformer 182. For one embodiment of the present invention, that timeis on the order of about 5 microseconds. As long as the ON time of theswitch 180 stays under that range, the transformer 182 will notsaturate. The magnetic flux density of the transformer 182 is determinedin part by design, geometry, and material selection of the componentsused in the construction of the transformer 182. Specifically, when theswitch or switches 180 turn on, the transformer 182 transfers energy tothe load 22. When the switch 180 is turned off, the field collapses andthe magnetizing energy is returned to the front end reservoir section asthe transformer core resets. FIG. 4( a) shows the MOSFET switch drainvoltage during a single cycle of operation. The switch is turned on atT0. The drain switches to 0V conducting current through the primary ofthe transformer. It is at this time that current flow is induced in thetransformer secondary and power is delivered to the load. At T1 theMOSFET switch is turned off. In the period from T1 to T2 the resultantresonant circuit voltage resets the transformer core. The resonantcircuit determines the reset time and consists of circuit reactancesincluding the Miller capacitance of switch 180, the inter-windingcapacitance of the transformer 182, and the primary inductance of thetransformer 182. The period of this reset time is approximately equalto: π√(L_(p)·C_(Q1)) Where L_(p) is the transformer primary inductanceand C_(Q1) is the circuit capacitance.

In one embodiment, the switch not be active during this reset periodsuch that the next pulse does not occur until the resonant reset of thecore of transformer 182 is complete. Therefore the reset time is afactor in the maximum pulse frequency delivered to the lamp. The numberof MOSFETS used in a given switch section determines the outputimpedance of the amplifier 20 (more MOSFETS equals lower outputimpedance). However, an increase in the number of MOSFETS causes anincrease in the reset time thus limiting the operating frequency(lengthening the PWM period). Since the most efficient transfer ofenergy to the lamp occurs when the amplifier 20 and lamp impedances arematched, the number of MOSFET switches used is important. The switchsection impedance is determined by the transformer design, the MOSFETswitch characteristics and the number of MOSFET switches used. Theamplifier 20 output impedance is also a function of the number ofamplifier 20 modules used and the connection configuration of thesemodules (series, parallel, or combination). There is a series of designtradeoffs between the lamp design, transformer design, MOSFET switchcharacteristics, and module configuration all of which must be balanced.

In a typical resonant switching amplifier, the energy per pulse is fixedand is determined by the resonance of the switch capacitance,transformer reactances, and reflected reactance from the transformersecondary and load 22. Varying the operating frequency of a resonantamplifier controls the output energy. The output energy is thentypically rectified, stored in a capacitor, then delivered to the load22. Regulation is provided by feedback which is used to vary theamplifier operating frequency in response to load 22 requirements.

In a typical non-resonant switching amplifier, the switch drive time isvaried (PWM) to vary the energy delivered per pulse and the PWM period(or frequency) remains fixed. The output energy is typically rectified,stored in a capacitor, then delivered to the load 22. Regulation may beprovided by feedback which is used to vary the switch on time (PWM dutycycle) in response to load 22 requirements. The present inventionrectifies but does not filter the output energy. Pulse energy (PWM) isdelivered directly to the load 22. The present invention can use bothpulse timing and frequency modulation to control energy delivered to theload 22.

Traditional resonant power supplies cannot provide variable energy perpulse. Rather the energy per pulse is fixed requiring fewer pulses perunit time be delivered to reduce output energy and more pulses per unittime to increase energy. This method in effect removes pulses which willcause the flash lamp to extinguish at low energy levels. Traditional PWMcontrolled power supplies use switch on time duty cycle to controlenergy and thus offer limited control range.

One embodiment of the present invention comprises the method of varyingthe pulse width as it would be in a non-resonant amplifier, but in thiscase, it is applied to MOSFETs. What makes this difficult is the gatecapacitance inherent in MOSFETs, which must be overcome in order tocontrol the switching. To vary the duty cycle, the MOSFET gate drive inthe present embodiment should have a rise time of 100 nS or less.Furthermore, the gate capacitance of the MOSFETs is additive, whichmeans that as the number of MOSFETs increases, the capacitive loadingalso increases. The present invention overcomes the gate capacitancewith a high speed, current amplifier (Q4 in FIG. 5). The currentamplifier provides a large amount of current at a high slew rate toswitch the MOSFET quickly. Specialized IC's can also provide high speedMOSFET gate drive.

The present invention, in one embodiment, uses a resonant reset, forwardconverter power topology, operating in a discontinuous mode. The outputof this amplifier 20 is controlled using pulse width modulation (PWM).The amplifier 20 can also be controlled with frequency modulation or acombination of frequency modulation and PWM. The present invention canuse this scheme to synthesize any type of current envelope directly tothe load 22. When used with a lamp, the present invention relies in parton the persistence of the lamp to do part of the filtering andintegration of the output pulses from the amplifier 20 to create asmoothed output. Diodes in known devices do not integrate these pulses.With the present topology, driving the amplifier 20 in this mode isaccomplished in part by having the following elements. The drive circuitthat drives the MOSFETs 180*80. It includes a drive transformer and aplurality of other switches. The maximum time that the energy istransferred to the load 22 (‘ON’ time) is determined by the transformerdesign and switch design such that primary transformer current isinterrupted before the transformer core is saturated. The maximumoperating frequency is determined by the sum of the ‘ON’ time and theresonant reset time.

In some embodiments, the physical elements may include a flash lamp orsome intermediate device to integrate the PWM output, any type of highspeed switch (in this embodiment is the MOSFET 180), and an energytransfer media (MOSFET 180+transformer 182). In one embodiment, the highspeed switch section 160 may deliver a plurality of pulses, each with avery small amount of energy to the flash lamp. The transfer medium usedin combination can vary the amount of energy by varying energy contentin each energy pulse. Because of this variability, this pulse formingnetwork can synthesize any waveform and is not locked into a particularwaveform. There is a significant cost reduction using the presentinvention since hardware does not need to be altered to generate newwaveforms and there is substantially greater flexibility in waveformsavailable. In one embodiment, the energy per pulse is variable at a 200Khz rate. From pulse to pulse, the present invention can vary theenergy. This gives the ability to generate any waveform with agranularity of 100 kHz, or 200 kHz (assuming 2 amps are used at 100khz), etc. In the present embodiment, the load 22 can be used tointegrate the envelope of pulses.

Referring to FIG. 5, a more detailed embodiment of the present inventionwill now be described. The embodiment of FIG. 5 includes a plurality ofMOSFET switches 180. In some embodiments, it is desirable to increasethe output from the amplifier 20 to achieve energy levels sufficient forhigher intensity uses. One technique for increasing the energy outputincludes adding more MOSFET switches to the inverter topology as seen inFIG. 5.

Again, in the present embodiment, a portion of a resonant amplifier 20topology is used. It should be understood that in some embodiments, thepresent invention may be described as having a resonant reset topology.Specifically, the present invention uses the reset portion of theresonant amplifier 20 and provides a transformer/inductor 182. As seenin FIG. 5, the switch section 160 includes a plurality of MOSFETswitches 190, 192, 194, 196, 198, and 200. These switches 190-200 arecoupled in a parallel configuration between elements of an input sectionand the energy transfer device, transformer 182.

When the switch or switches in section 160 are ON, energy is transferredenergy through the transformer 182 to the load 22. When the switchsection is turned off, the transformer core is reset by imposing aresonant voltage on the primary winding using the magnetizing energy inthe transformer core is returned to the front end reservoir sectionthrough diode CR4 while resetting the core of transformer 182. It shouldbe noted that, in the embodiment of FIG. 5, there is no current flowthrough the switches while the switches are transitioning from ON toOFF.

As a nonlimiting example, the design determines that in one embodiment,a switch that can handle 100 amps average and 600 amps peak is desired.This results in a total miller capacitance of 6 nF, so a primaryinductance is desired of a small enough amount so the two of thosetogether have a time constant that does not violate the fixed operatingfrequency desired to keep above the persistence time of the flash lamp.If 100 KHz operation is desired (10 μS period), and 5 μS energy pulseduration is desired, then the maximum allowable rest time is 5 μS. Usingthe resonance formula π√(L_(p)·C_(Q1)) and solving for inductance(L_(p)), the primary inductance in the present embodiment should notexceed 420 uH. Some embodiments may desire to keep above 10 times thepersistence time of the flash lamp. The resonant period should fitwithin the pulse width modulation frequency.

FIG. 5 shows more detail with regards to other elements used in theinput section 140, switch section 160, and output section 170. As seenin FIG. 5, the input section 140 contains a scaling amplifier 20, pulsewidth modulator and output driver. The scaling amplifier 20 amplifiesthe input signal to adequately drive the pulse width modulator whichfollows. The pulse width modulator is an oscillator in which the on timecan be varied in response to the input signal. The pulse width modulatorproduces a fixed frequency square wave of which the on time is variedproportionately to the input signal. The output driver provides currentamplification adequate to provide drive to the switch section.

The switch section 160 (described in detail in the previous paragraphs)provides energy transfer to the load 22 and ensures electrical isolationfrom the load 22.

The output section consists of the transformer secondary, isolationdiodes and balancing resistors. The output section couples the energy tothe load 22 and together with the switch section, provides impedancematching with the load 22. The transformer provides the coupling ofenergy from the switch section to the output and also provides theelectrical isolation from the switch section and load 22. The isolationdiodes prevent reversed current flow to the load 22 during thetransformer core reset period. The isolation diodes also prevent currentflow from one module to another module when multiple modules areconnected to one load 22. The transformer and diode isolation makes itpossible to connect multiple modules to one load 22.

The control section consists of logic circuitry which can supervise theoperation of the overall amplifier 20. The control section can monitorload 22 current and limit the PWM duty cycle to a preset maximum value.The control section can also provide an arbitrary signal to the inputscaling amplifier 20 to drive the load 22 with a synthesized arbitrarywaveform. The control section can also vary the PWM frequency for lowpower applications.

The present invention can withstand a load 22 of varying amount. Thefeature that allows the amplifier 20 to withstand the negative impedanceis that the sensitive element (the switch) is not involved directly inthe transfer of energy into the load 22. Zero current switching isdesirable. The energy is transferred by the transformer. So, it istransferred magnetically. Then the switch is turned off and the switchhas a period time for it to turn off. The period of time is determinedby its miller capacitance and the inductance of the transformer. Noenergy is transferred during the switching.

Thus as seen in FIG. 5, some embodiments of the present invention may beviewed as having a switch section, an output section having atransformer, isolation circuitry, and snubber circuitry. The presentinvention may include rectifiers (diodes) so that energy only goes tothe load 22. The persistence of the load 22 may be a design constraintthat will influence the selection of these elements. It should beunderstood that in some embodiments, the lower the amplifier 20 outputimpedance, the better. The ability to drive in parallel and series isdesirable in some embodiments.

Referring now to FIG. 6, a schematic showing an amplifier 20 using asingle inverter section is shown. As seen, input and PWM drive sectionsprovide the inverter section (having the switch section and the outputsection) to provide a pulsed output directly to the load 22.

Referring now to the embodiment of FIG. 7, it should be understood thata parallel configuration may be used, having two inverter sections. Thisdecreases the output impedance of the amplifier 20. This will increasethe amplitude of the output pulse to a dynamic load 22 such as but notlimited to a flash lamp. The output section provides the isolation andallowing for connection of parallel switch sections. Transformers andswitches may be added in the manner to improve performance.

Referring now to the embodiment of FIG. 8, a still further variationshows that two inverter sections may be connected in parallel but drivenin series. As seen, the input from the input and drive sections are outof phase. Specifically, they are driven out of phase by 180 degrees.This results in the delivery of pulses to the lamp or load 22 twice asoften, effectively doubling the power delivered to the load 22. In thepresent embodiment, about 80 kHz-100 kHz is a design range for thefrequency of the amplifier 20. Such circuit has a resonant reset periodof about 5 microseconds. There is only a certain amount time that energycan be stored in the device before the magnetic flux density is depletedand the storage saturates. 5 microseconds is the time before the deviceis turned off and allowed to reset. Thus, for this particularembodiment, one cannot put as much into this transformer core at thisoperating frequency. If the frequency is decreased, one can store moreenergy per pulse, deliver more to the load 22. This brought about theseries configuration as described in FIG. 8. In one nonlimiting example,the power supplies may operate at 70 khz, but the lamp will receivetwice as many pulses (140 khz drive) since there are two amplifiers 20supplying pulses out of phase.

FIG. 9 shows a combination of amplifiers 20 coupled together in a seriesand parallel drive configuration. It should be understood that thesechanges in driving the amplifiers 20 does not change the physical oractual connection to the lamp. Most of these changes occur in software.

Referring now to the embodiment of FIG. 10, a still further variationshows that the outputs of two inverter sections may be connected inseries but driven in parallel. This increases the output voltagedelivered to the load 22.

The power supplies of the present invention may be advantageously usedin a variety of applications. As a nonlimiting example, the embodimentsof the present invention may be used to address the issue of thermallensing that occurs in laser systems. Thermal lensing is undesirable asit changes the operating parameters of the laser. Although not limitedto the following, the present example uses a YAG laser operating at 10hz. The present method involves maintaining a constant thermal load onthe gain medium over a period of time. Thus, even though the rep rate ofthe laser may vary, the amount of energy delivered to the rod or gainmedium is the same over a period of time. In this way, thermal lensingdoes not change since the thermal load does not change.

Referring now to FIGS. 11-13, in one embodiment of the presentinvention, this may involve extending pulse duration to maintainconstant thermal loading. The pump conditions may be adjusted so thatthe amount of energy delivered to the gain medium over a period time ofX is always constant. In FIG. 11, the period of is 2 t. The pulses areadjusted and Q-switched to achieve the desired energy output and reprate. Because the pulse width is variable, it can be adjusted with therep rate to maintain the same thermal load on the gain medium. Thepresent invention provides a thermal load of N per pulse and the loadingwould be N divided by frequency per pulse. FIG. 11 shows that energy isprovided to the gain medium over a period of time from 0 to 0.5 t and 1t to 1.5 t. The laser is Q-switched at the end of each pulse. In FIG.12, the same amount of energy is delivered to the gain medium asindicated by pulses 300 and 302. The Q-switch may be varied to changethe rep rate and/or energy from the laser, but the thermal load on thegain medium remains the same over the same period of time as that inFIG. 11. FIG. 13 shows that the rep rate is increased, but again, thetotal amount of energy seen by the gain medium is the same and thethermal loading over the time 2 t in FIG. 13 is the same as the thermalloading in FIG. 11.

The constant thermal load may be accomplished, in one embodiment, byQ-switching the laser to deliver the laser light but still allowingenergy to heat the rod after the Q-switch. After the buildup, theQ-switch is fired. In one example, the laser fires at 10 hz, so if 25joules are put into the laser 10 times a second (250 watts), about 2.5watts come out as laser light (e.g. about 1% comes out). The remaindergoes to heat the YAG laser rod. The problem with all YAG lasers is thatthey are fixed point operating systems. With more heat, the lense getssharper, with less heat the lense is less sharp. The thermal lense is afunction of rep rate and corrective optic. Different laser rods havedifferent thermal lenses.

With the present invention, the amplifier 20 can maintain constantthermal loading or constant watts. As a nonlimiting example, if thelaser operates at 50 hz (200 ms), 1250 watts are put into the laser persecond. This creates a very sharp lense since there is substantialheating in the rod. Typically, changing the frequency of the laser willchange the thermal load on the laser and result in a different thermallensing to correct for. The present invention may be used to maintain aconstant thermal lens, even when the laser operates at varying rep rate.The amplifier 20 may vary its output to maintain the constant thermalload, while also adjusting for varying rep rates for the laser. Thelaser may be Q-switched to deliver the laser energy at a desiredfrequency. However, the remainder of the time, the amplifier 20 will beused to deliver energy to the rod to keep the rod warm. Thus in thepresent example, if the laser operates at 12 hz, the YAG rod still sees1250 watts. The Q switch may occur every 12th pulse, but again the heatload on the laser rod remains the same since the same amount of energyis still delivered to the laser rod. The Q switching is varied. FIG. 14shows another embodiment where the Q-switch occurs at a lower rep rate.Again, the thermal load over the period 2 t is the same in FIG. 11 andin FIG. 14.

While the invention has been described and illustrated with reference tocertain particular embodiments thereof, those skilled in the art willappreciate that various adaptations, changes, modifications,substitutions, deletions, or additions of procedures and protocols maybe made without departing from the spirit and scope of the invention.For example, with any of the above embodiments, a variety of protectionelements may be included in the circuit design to minimize heating ofthe elements. In some embodiments, the present invention may be viewedas having two elements (switch+transformer) with a certain result in aresonant topology. Embodiments of the present invention may use gappedor ungapped transformers. It should be understood that some embodimentsmay have output energy is typically rectified, stored in a capacitor,then delivered to the load 22. For other applications using any of theembodiments described herein, other light sources can be powered.Incandescent, fluorescent lamps, diodes, LEDS, metal vapor lamps, andother light sources can be powered by the amplifier 20 according to thepresent invention.

The publications discussed or cited herein are provided solely for theirdisclosure prior to the filing date of the present application. Nothingherein is to be construed as an admission that the present invention isnot entitled to antedate such publication by virtue of prior invention.Further, the dates of publication provided may be different from theactual publication dates which may need to be independently confirmed.All publications mentioned herein are incorporated herein by referenceto disclose and describe the structures and/or methods in connectionwith which the publications are cited. The present application is acontinuation in part of U.S. Ser. No. 11/053,194 filed Feb. 7, 2005, andis a continuation-in-part of U.S. Ser. No. 11/053,195, filed Feb. 7,2005, both of which applications claim the benefit of priority fromcommonly assigned co-pending U.S. Provisional Application Ser. No.60/569,207 filed May 6, 2004. All of the above-identified applicationsare fully incorporated herein by reference for all purposes.

Where a range of values is provided, it is understood that eachintervening value, to the tenth of the unit of the lower limit unlessthe context clearly dictates otherwise, between the upper and lowerlimit of that range and any other stated or intervening value in thatstated range is encompassed within the invention. The upper and lowerlimits of these smaller ranges may independently be included in thesmaller ranges is also encompassed within the invention, subject to anyspecifically excluded limit in the stated range. Where the stated rangeincludes one or both of the limits, ranges excluding either both ofthose included limits are also included in the invention.

While the above is a description of the certain embodiments of theinvention, various alternatives, substitutions and modifications may bemade without departing from the scope thereof, which is defined by thefollowing claims. Thus, the preferred embodiments should not be taken aslimiting the scope of the invention. Furthermore, the present inventionis directed to a number of separate inventions and each of theseinventions may be claimed independently of one another. Each feature,aspect and advantage of the invention may be claimed independent of oneanother without departing from the scope of the invention. Thus, theinvention does not include a single essential feature, aspect oradvantage and the invention should not be limited as such. It isintended, therefore, that the invention be defined by the scope of theclaims which follow and that such claims be interpreted as broadly as isreasonable.

1. A power supply system of a pulse forming network that includes anamplifier, comprising: a power supply; at least one energy storagecapacitor bank; a voltage monitor coupled to the power supply and theenergy storage capacitor bank; a feedback control coupled to the powersupply, the feedback control configured to provide a measurement of anamount of energy that is delivered to the pulse forming network; and inresponse to the measurement, the feedback control going to a highresolution mode where it maintains an amount of energy stored in thepulse forming network to compensate for internal losses within the pulseforming network that occur through component imperfections, the feedbackcontrol configured to provide that a current applied to the energystorage capacitor bank is substantially the same as current leaking outof the power supply.
 2. The system of claim 1, wherein the feedbackcontrol includes control logic.
 3. The system of claim 1, wherein thefeedback control includes a precision control device.
 4. The system ofclaim 1, wherein the output of the power supply is rectified and used tocharge the at least one energy storage capacitor bank.
 5. The system ofclaim 1, wherein the system is a low repetition rate system.
 6. Thesystem of claim 1, further comprising: an amplifier driver that drivesthe amplifier in a discontinuous mode, and during a non-energy transferportion, the output of the amplifier is electrically isolated from theload, wherein the electrical isolation allow for coupling multipleamplifier outputs together, the amplifier driver including logic fordriving the amplifiers in a manner selected from at least one of: 1)increasing power by interleaving the drive of multiple amplifier modulesor 2) lowering the impedance by simultaneously driving the connectedamplifier modules.
 7. The system of claim 1, wherein the amplifierincludes a number of switches that influence an absolute reset time forthe amplifier, and the number of switches is selected so as not to causethe reset time of the amplifier to exceed 1/10th of the persistence timeof the lamp.
 8. The system of claim 1, wherein an output voltage isselected so that wavelength output from the dynamic load issubstantially in the infrared wavelengths.
 9. The system of claim 1,wherein an energy output of the amplifier is proportional to an analoginput, the energy output having a plurality of pulses, the amplifierhaving an output recovery time sufficiently fast to enable another pulseto be delivered to the load prior to exceeding a persistence time of theload.
 10. The system of claim 1, wherein the amplifier has a topologythat provides during a non-energy transfer portion that an impedance isat a level such that an amplifier output current is limited from theamplifier and a peak current of a switch in the amplifier does notexceed a peak current rating of the switch.
 11. The system of claim 1,wherein the amplifier has a topology that provides during a non-energytransfer portion, an output of the amplifier is electrically isolatedfrom the load.
 12. The system of claim 1, wherein the PWM power outputis directly to the non-linear load, and the amplifier has a topologyconfigured to provide during a non-energy transfer portion an impedancegreater than 10000 times a minimum, dynamic impedance of the non-linearload.
 13. The system of claim 1, further comprising: an amplifier driverto drive the amplifier in a discontinuous mode; and wherein theamplifier has a topology to provide that an output of the amplifier iselectrically isolated from the non-linear load during a negativeimpedance state and tolerates a negative impedance of the load.
 14. Thesystem of claim 1, further comprising: an amplifier driver to drive theamplifier in a discontinuous mode, and during a non-energy transferportion an output of the amplifier is electrically isolated from theload, the electrical isolation providing for coupling multiple amplifieroutputs together, the amplifier driver having logic for driving theamplifiers in a manner selected from at least one of: 1) increasingpower by interleaving the drive of multiple amplifier modules or 2)lowering the impedance by simultaneously driving the connected amplifiermodules; an amplifier providing a PWM power output to the non-linearload, the amplifier comprising a plurality of amplifier modules eachproviding a power output.
 15. A power supply system, comprising: a powersupply; at least one energy storage capacitor bank; a voltage monitorcoupled to the power supply and the energy storage capacitor bank; afeedback control coupled to the power supply, the feedback control andprecision control device configured to provide that a current applied tothe at least one energy storage capacitor bank is substantially the sameas current leaking out of the power supply; a dynamic load having adynamic load impedance; an amplifier that has as part of the amplifier aresonant reset topology, the amplifier being configured to vary a dutycycle in response to a signal resented to an input; and wherein theamplifier has an output impedance that is less than the dynamic loadimpedance of the dynamic load when the dynamic load is in a confineddischarge mode.
 16. The system of claim 1, wherein the amplifier has atopology that provides for, during a non-energy transfer portion, animpedance at a level such that the amplifier output current is limitedfrom the amplifier such that the peak current of a switch in theamplifier does not exceed the peak current rating of the switch.
 17. Thesystem of claim 1, wherein the amplifier has a topology configured toprovide that during a non-energy transfer portion an output of theamplifier is electrically isolated from the load.
 18. The system ofclaim 1, wherein the amplifier has a topology configured to provide thatan output of the amplifier is electrically isolated from the dynamicload during a negative impedance state and tolerates a negativeimpedance of the load.
 19. A power supply system of a pulse formingnetwork that includes an amplifier, comprising: a power supply; at leastone energy storage capacitor bank; a voltage monitor coupled to thepower supply, and the energy storage capacitor bank; a feedback controlcoupled to the power supply, the feedback control and configured toprovide that a current applied to the at least one energy storagecapacitor bank is substantially the same as the current leaking out ofthe power supply; wherein the amplifier includes a number of switchesthat influences an output impedance of the amplifier, and the number ofswitches is selected so that the impedance is less than or equal to thedynamic load impedance the amplifier having a resonant reset topology.20. The system of claim 19, wherein the switches are MOSFET switches.21. A power supply system of a pulse forming network that includes anamplifier, comprising: a power supply; at least one energy storagecapacitor bank; a voltage monitor coupled to the power supply and theenergy storage capacitor bank; a feedback control coupled to the powersupply the feedback control and configured to provide that a currentapplied to the at least one energy storage capacitor bank issubstantially the same as the current leaking out of the power supply;wherein the amplifier includes a transformer with magneticcharacteristics that influence an absolute reset time of the amplifier,the magnetic characteristics being selected to provide that a reset timeis less than or equal to a desired percentage of a persistence time ofthe dynamic load.
 22. A power supply system of a pulse forming networkthat includes an amplifier, comprising: a power supply; at least oneenergy storage capacitor bank; a voltage monitor coupled to the powersupply and the energy storage capacitor bank; a feedback control coupledto the power supply, the feedback control and configured to provide thata current applied to the at least one energy storage capacitor bank issubstantially the same as the current leaking out of the power supply;wherein the amplifier includes a transformer made of a core materialthat influences an absolute reset time of the amplifier, the corematerial being selected to provide that an absolute reset time of theamplifier is less than or equal to a desired percentage of a persistencetime of the dynamic load.
 23. A power supply system of a pulse formingnetwork that includes an amplifier, comprising: a power supply; at leastone energy storage capacitor bank; a voltage monitor coupled to thepower supply and the energy storage capacitor bank; a feedback controlcoupled to the power supply, the feedback control and configured toprovide that a current applied to the at least one energy storagecapacitor bank is substantially the same as the current leaking out ofthe power supply; wherein the amplifier has a resonant reset, forwardconverter topology, and includes a transformer with windings thatprovide a certain number of gauss, and the number of windings affectsthe rise time of the transformer, wherein a rise time is selected sothat such that an absolute reset time of amplifier is less than or equalto a desired percentage of a persistence time of the dynamic load orsaturation time.
 24. A power supply system, comprising: a power supply;at least one energy storage capacitor bank; a voltage monitor coupled tothe power supply and the energy storage capacitor bank; a feedbackcontrol that includes control logic; and a precision control devicecoupled to the feedback control and the power supply, the feedbackcontrol and precision control device configured to provide that acurrent applied to the at least one energy storage capacitor bank issubstantially the same as current leaking out of the power supply; adynamic load having a dynamic load impedance; an amplifier having aresonant reset topology configured to provide a PWM power output to thedynamic load, wherein the amplifier has an output impedance that is lessthan the impedance of the load when the load is in a confined dischargemode; a flash lamp having a flash lamp impedance and an arc persistencetime when the flash lamp is lit, the amplifier having a topology forproviding PWM power output directly to the flash lamp; and an amplifierdriver configured to drive the amplifier, the amplifier driver having afixed or variable frequency control that provides the PWM power outputat a frequency such that the period of the power output does not exceedthe persistence time of a flash lamp during energy delivery.
 25. Thesystem of claim 24 wherein the amplifier driver is configured to drivethe amplifier to provide a PWM output at a frequency of no slower than1/10th of a persistence time of a flash lamp.
 26. The system of claim24, wherein the amplifier driver is configured to drive the amplifier toprovide a PWM output at a frequency of no slower than a desiredpercentage of a persistence time of a flash lamp, the frequency selectedso that an optical output of the flash lamp has less than 10% ripple.27. The system of claim 24, wherein the amplifier has an outputimpedance that is less than the impedance of the lamp when the lamp isin a confined discharge mode.
 28. The system of claim 24, wherein, anoutput impedance of the amplifier is less than 1/10 of the impedance ofthe lamp when the lamp is in a confined discharge mode.
 29. The systemof claim 24, wherein an output impedance of the amplifier is less than1/50 of the impedance of the lamp in a confined discharge mode.
 30. Thesystem of claim 24, wherein the amplifier has a topology to provide thatduring a non-energy transfer portion, the impedance is at a level suchthat an amplifier output current is limited from the amplifier such thatthe peak current of a witch in the amplifier does not exceed the peakcurrent rating of the switch.
 31. The system of claim 24, wherein theamplifier has a topology that provides during a non-energy transferportion, the output of the amplifier is electrically isolated from theload.
 32. The system of claim 24, wherein the amplifier has a topologythe provides during a non-energy transfer portion, the amplifier has animpedance greater than 10000 times a minimum, dynamic impedance of theflash lamp.
 33. The system of claim 24, wherein the amplifier has atopology o provide that the output of the amplifier is electricallyisolated from the flash lamp during a negative impedance state andtolerates a negative impedance of the load.
 34. The system of claim 24,wherein the amplifier has a plurality of amplifier modules eachproviding a power output, and the amplifier driver provides for drivingthe amplifier in a discontinuous mode, and during a non-energy transferportion, the output of the amplifier is electrically isolated from theload, wherein the electrical isolation allow for coupling multipleamplifier outputs together, the amplifier driver including logic fordriving the amplifiers in a manner selected from at least one of: 1)increasing power by interleaving the drive of multiple amplifier modulesor 2) lowering the impedance by simultaneously driving the connectedamplifier modules.
 35. The system of claim 24, wherein the amplifierincludes a number of switches that influences an output impedance of theamplifier, and the number of switches is selected so that the impedanceis less than or equal to the flash lamp impedance.
 36. The system ofclaim 35, wherein the switches are MOSFET switches.
 37. The system ofclaim 24, wherein the number of switches is selected so as not to causethe reset time of the amplifier to exceed 1/10th of the persistence timeof the lamp.
 38. The system of claim 24, wherein the amplifier has atransformer with magnetic characteristics that influence an absolutereset time of the amplifier, and the magnetic characteristics areselected so that the reset time is less than or equal to a desiredpercent of a persistence time of the flash lamp.
 39. The system of claim24, wherein the amplifier has a transformer made of a core materialwhich influences an absolute reset time of the amplifier, the corematerial selected so that such that the absolute reset time of amplifieris less than or equal to a desired percentage of a persistence time ofthe flash lamp.
 40. The system of claim 24, wherein the amplifier has atransformer and windings that provide a certain number of gauss and thenumber of windings affects the rise time of the transformer, and therise time is selected so that such that the absolute reset time ofamplifier is less than or equal to a desired percentage of a persistencetime of the flash lamp or saturation time.
 41. The system of claim 24,wherein the amplifier has a resonant reset, forward converter topology,and an output voltage is selected so that wavelength output from theflash lamp is substantially in the infrared wavelengths.
 42. The systemof claim 24, wherein energy output of the amplifier is proportional tothe analog input, the energy output comprising a plurality of pulses,the amplifier having an output recovery time sufficiently fast to enableanother pulse to be delivered to the load prior to exceeding apersistence time of the load.
 43. The system of claim 24, wherein theamplifier hays a topology wherein during a non-energy transfer portion,the impedance is at a level such that the amplifier output current islimited from the amplifier such that the peak current of a switch in theamplifier does not exceed the peak current rating of the switch.
 44. Thesystem of claim 24, wherein the amplifier has a topology that providesduring a non-energy transfer portion, the output of the amplifier iselectrically isolated from the load.
 45. The system of claim 24, whereinthe amplifier has a topology configured to provide that during anon-energy transfer portion, the amplifier has an impedance greater than10000 times a minimum, dynamic impedance of the non-linear load.
 46. Thesystem of claim 24, wherein the amplifier driver drives the amplifier ina discontinuous mode, and the amplifier has a topology that provides foran output of the amplifier to be electrically isolated from a non-linearload during a negative impedance state and tolerates a negativeimpedance of the load.
 47. The system of claim 24, wherein the amplifierdriver drives the amplifier in a discontinuous mode, and during anon-energy transfer portion, the output of the amplifier is electricallyisolated from the load, the electrical isolation allowing for couplingmultiple amplifier outputs together, the amplifier driver includinglogic for driving the amplifiers in a manner selected from at least oneof: 1) increasing power by interleaving the drive of multiple amplifiermodules or 2) lowering the impedance by simultaneously driving theconnected amplifier module.